CDI ?.... MSD ?..... Help please

mycar · Post by **mycar** » Wed Jul 16, 2008 9:42 pm

I was hoping that by the time I got to my age I`d pretty well know all I`d need to know about.... well... everything.

B*GGER

A Satuday afternoon at Mike Bainbridges revealed yet another gaping hole in my education...... namely, ignition systems.

So this week I`ve mainly been reading up about coils and capacitors... and I`m making a bit of progress, to the stage where I`d like to ask for some opinions.

Mycar has the original ignition system and my question is should I be thinking of `upgrading` it to a 3 pin CDI.... or even MSD?

I`ve been trawling Pelican and threads like Jamies here on DDK and there seems to be a whole load of pros and cons.... reliability of the later electronics....cost... availability( of the CDI).... and originality issues

It seems reasonable to suppose that, as the 2.0 s engine does it`s best work at the top end of it`s rev band, it seems a shame to ignite it with a system which actually struggles to charge and discharge fast enough when it counts.

Your views would be appreciated.

Regards, Mike

Bertroex · Post by **Bertroex** » Wed Jul 16, 2008 10:12 pm

If I were you, I'd listen to Mike Bainbridge

Bert

mycar · Post by **mycar** » Wed Jul 16, 2008 10:42 pm

Bertroex wrote:If I were you, I'd listen to Mike Bainbridge

Bert

Trust me, I did. Mike told me all about it but at the time it all went a bit over my head (a lot). It`s just that now, I`m trying to make sense out of it without bothering him too much.

Mike.

Barry · Post by **Barry** » Wed Jul 16, 2008 11:19 pm

Well, I can certainly vouch for MSD: pretty reliable, new (as opposed to 30 yr+ CDI boxes), very easy starting and smoother idling.

Downsides? Not much really, you can still trigger with points, but you should ideally upgrade your HT leads to reduce interferance and leakage. I used Turbo leads and plugs. The MSD intructions say that these leads are essential, but I think we concluded this was for American legal purposes, rather than entirely for performance. You would need a matching coil (as you would for a CDI system also). The only other thing to watch is that you may need a tacho-driver. I gather some tacho's do, and some don't. I did.

Anyway, I put mine on nearly four years ago (I think) and it's still fine (according to James 'TheEasyLife'), certainly don't regret fitting it, and would be happy to do so again.

Charlotte's 911 is now running twin MSD's, and had a single unit before that, and also Steve Wright is also running twin MSD's as well.

The MSD 6A was the basic unit with no (I think) rev limiter, but most people use the 6AL which has plug-in rev tabs, giving a pre-programmed soft-rev limiter. I gather even this has been updated, with a mappable unit now being available.

pb911 · Post by **pb911** » Thu Jul 17, 2008 12:09 am

i did this and didnt look back !:

Remove your distributor, and never look back
...with the XDi Distributorless Ignition System!

Crank-fired accuracy
Control Module and coils
Full spark energy to 15,000 rpm
No computer required for tuning!

Electromotive, Inc., originators of the High Resolution Electronic Ignition Circuit, introduce the next generation High Performance Ignition System: the XDi. With an amazing 0.1 degree timing accuracy, the XDi is the most accurate ignition available. An integral rev-limiter can be set anywhere between 4,000 and 15,000 rpm. For drag racing an additional rev-limiter can be wired for staging and burnouts. For street applications, MAP sensors can be integrated to supply a "vacuum-advance". This allows increased ignition advance when under light load. Engines running single-stage nitrous oxide setups can benefit from the XDi's built-in timing retard feature. Engines running multiple stages of nitrous can use the Electromotive 4-Stage Nitrous Timing Retard module with the XDi.

The beauty of the XDi distributorless ignition system is its simplicity. To obtain engine speed and crank position, a 60-2 tooth trigger wheel is attached to the crankshaft, and a magnetic sensor is aimed at the wheel. Knobs adjust the spark advance at different engine speeds; NO computer required. A robust machined aluminum casing houses the electronics and provides a solid mount for the coils. The XDi can be mounted under the hood making it an easy system to adjust and maintain.

Electromotive offers custom XDi kits for popular domestic and import applications. These kits include trigger wheel, magnetic sensor, and sensor bracket for a easy installation.

XDis are currently available for 4-, 6- and 8-cylinder, single- or dual-plug engines, and 2- or 3-rotor rotary applications.

See Ignition Systems

Mike911scrs · Post by **Mike911scrs** » Thu Jul 17, 2008 6:04 pm

HI Barry
"Charlotte's 911 is now running twin MSD's" is actualy only has 1 MSD box running 2 MSD coils.

regards mike

TimB · Post by **TimB** » Thu Jul 17, 2008 9:32 pm

Mike
PM sent.
Regards
Tim

Barry · Post by **Barry** » Thu Jul 17, 2008 10:57 pm

Hi Mike: that's impressive, I didn't know you could do that. Shows how much those units have in reserve.

Nevertheless, I'm pretty sure (for what it's worth

) that Steve Wright is using two systems.

Ian Donkin · Post by **Ian Donkin** » Thu Jul 17, 2008 11:01 pm

... and I might yet buy another (not that there's anything wrong with how it's working now) to fire each coil from its own MSD box.

The curent setup is how Henry at Supertech recommends you do it, whilst the boys at JB Racing did suggest two MSD boxes.

As you can see, Mike was happy to run the system with just one box.

Decisions, decisions!

Barry · Post by **Barry** » Thu Jul 17, 2008 11:05 pm

How does the MSD fire both coils: do you literally split the MSD output to fire the coils in parallel (i.e. loop the output wire into one coil, and onto the next), or are there some MSD's with twin outlet wires?

Ian Donkin · Post by **Ian Donkin** » Thu Jul 17, 2008 11:09 pm

Neither - split the MSD output and feed each coil from one lead of the splitter (see the white and red wires in the picture from Mike above).

Barry · Post by **Barry** » Thu Jul 17, 2008 11:09 pm

Also, if you run two coils from one MSD, does this mean that the Multiple Spark phase cuts out earlier than it would with the system'just' running six plugs rather than twelve?

Or to put it another way, with twin MSD usnits in place, would you get the benefits of the Multiple Sparks for longer / higher up the rev-range?

Ian Donkin · Post by **Ian Donkin** » Thu Jul 17, 2008 11:10 pm

Pass!

Can I have the next question on Golf?

Lightweight_911 · Post by **Lightweight_911** » Thu Jul 17, 2008 11:17 pm

I opted to go for two MSD Blaster coils fired by two MSD 6AL's for my set-up after discussions with Steve Weiner (of Rennsport Systems in the US) - but mounted on a panel inside the car (on the rear bulkhead).

In the engine compartment I have two 'dummy' Bosch CDI boxes & two Bosch black coils to preserve the period-original look ...

Barry · Post by **Barry** » Thu Jul 17, 2008 11:18 pm

Ian Donkin wrote:Neither - split the MSD output and feed each coil from one lead of the splitter (see the white wires in the picture from Mike above).

Yes, that's parallel then: I'm amazed that the unit can take this, as effectlively it means that the internal gubbins must be 'engineered' (if that's what electronics are) to run either one or two coils with no physical switching, which is either very impressive, or just a worry for their warranty department

.

Nevertheless, I do know that MSD units have a name for operating in some dreadful conditions in some of the U.S. based applications, and doing so for long periods without trouble.

As per the above question (sorry Ian

), I'd love to know what dictates the cut in / out point of the multi-sparking function, before it drops into the big, single spark mode. I.e. whether this is simply a function of revs, or a function of stress upon the unit (more load, less multi-sparking).